Figure 7. Presynaptic Calcium Dynamics in the snph (+/+) and snph (−/−) Neurons.

(A) Representative calcium images at presynaptic boutons of the snph (+/+) and (−/−) neurons before stimulation (1), at the beginning (2) and the end (3), and after stimulation (4). Calcium transients within presynaptic boutons labeled with DsRed-monomersynaptophysin were imaged using Fluo-4NW at 50 ms intervals upon stimulation at 10 Hz for 10 seconds. The images are pseudocolored, with blue representing low [Ca²⁺] concentration and red representing high [Ca²⁺] concentration. Scale bars: 1 μm.

(B) The time course of changes in presynaptic fluorescent intensity over baseline (ΔF/F₀) from the snph (+/+) (black, n=32) and (−/−) (red, n=33) neurons. Inset: the peak values of intracellular [Ca²⁺] levels within boutons were averaged from last 10 stimuli (20 frames of calcium imaging), expressed as % increase of fluorescence intensity over baseline (ΔF/F₀), and are significantly different (p<0.001, t test) between the snph (+/+) (24%±2%) and (−/−) (33%±2%) neurons. Error bars: s.e.m.